1. Field of the Invention
This invention relates to dispensing fluid, and more particularly to a method and apparatus for dispensing fluid on demand in precisely measured quantity.
2. Description of Related Art
Many situations call for mixing pre-measured amounts of a fluid with other fluids, powders, etc. For example, pharmacists are frequently called upon to reconstitute medications, such as antibiotics for ingestion primarily by infants and small children. The medication typically is provided to the pharmacist as a powder or concentrate which must be reconstituted by mixing the antibiotic with filtered water. Pharmacists reconstitute the medication upon receipt of a prescription from a customer.
Traditionally, a pharmacist would have available a container of filtered water suitable for use in reconstituting medications. The pharmacist would measure the proper amount of filtered water to be used in reconstituting the medication by pouring the filtered water from a relatively large container into a graduated cylinder, or other such receptacle for measurement. The measured amount of filtered water would then be combined with the medication. Accordingly, the pharmacist must maintain a sufficient supply of filtered water. Furthermore, the pharmacist must maintain a set of graduated cylinders or other such receptacles for measuring filtered water. In addition, the process is relatively labor intensive.
It is common for pharmacists to purchase filtered water from a supplier rather than have a filter which can be used locally to filter tap water. Filtered water is typically purchased in containers that can be connected by tubing to a valve that allows the user to dispense the filtered water, thus making it more convenient for the pharmacist to dispense the water. The tube enters the container so that the water can be siphoned from the container. In order to cause the fluid to flow from the container, the container is typically placed at a relatively high elevation with respect to the point of delivery, to allow the fluid to be siphoned. The pharmacist must then gently orally suck on the dispensing end of the tube in order to prime the tube and allow the filtered water to flow. Once the tube has been primed, the flow of filtered water is commonly controlled by compressing the tube using a clip. This system presents several problems. First, having the pharmacist orally suck on the end of the tube contaminates the filtered water that then passes through the tube. Second, over time, purchasing filtered water is far more expensive than filtering tap water at the pharmacy. Third, the pharmacist must accurately measure the amount of water that is dispensed. Therefore, many pharmacists are installing water filter systems which provide the pharmacy with a ready supply of filtered water, without the need to suck on the end of a tube. However, the pharmacist must still accurately measure the amount of filtered water that is to be used to fill each prescription. Fourth, the tip from which water is dispensed typically comes into contact with the prescription. Therefore, there is a danger of cross-contamination. In addition, the tip may become dirty and contaminated from other foreign substances. Still further, due to the structure of the tip (i.e., the relatively thin passage through the tip), the tip is difficult to clean. Therefore, a bacterial build-up can occur within the tip.
In accordance with one system which is commercially available from Innovative Medical Services of San Diego, known as the "FillMaster", a water filter is coupled to a water dispenser which allows a pharmacist to open a first valve and release water under pressure from a pressurized holding tank within the filtration system into a graduated holding tank within a dispenser. The gradations on the graduated holding tank and the water level are visible to the pharmacist as the water fills the graduated holding tank. The pharmacist closes the valve once the graduated holding tank within the dispenser is holding the desired amount of filtered water. A second valve allows the filtered water within the graduated holding tank to be released into a container for use by the pharmacist. This system eliminates the need for the pharmacist to suck on the end of the dispensing tube. Furthermore, the filter provides filtered water which may be used in reconstituting medications.
Nonetheless, the pharmacist must be diligent in filling the graduated holding tank with the proper amount of filtered water. Still further, the filters within the filtration system must be replaced at regular intervals which depend upon one of three conditions: (1) time; (2) usage; and (3) purity of the water being output. Therefore, the pharmacist must maintain records as to when the filter was last serviced, must maintain records reflecting the amount of water which has been filtered since the last time the filter was serviced, and must regularly verify that the purity of the water is within acceptable tolerances. Furthermore, the proper method to be used to reconstitute a medication is first to add a portion of the total amount of filtered water to the medication; second to stir the medication and the filtered water; and third to add the remainder of the filtered water to the medication. It is very important that this process be followed when reconstituting a prescription for several reasons. For example, if the entire amount of fluid is dispensed at one time, the combination of fluid and the powdered antibiotic may overflow the container, since the total volume of fluid and powder is greater before mixing than after. If any portion of the prescription overflows the container, then the entire prescription must be discarded. In addition, for some medications, the powder may not properly dissolve if this proper procedure is not followed. There is currently no mechanism available for ensuring that the pharmacist performs this process properly (i.e., for ensuring that the pharmacist does not release the entire amount of filtered water at one time).
In addition, most medications are packaged in bottles that are coded (usually using the well-known "bar code" method) with information pertaining to the medication. For example, in addition to containing other specifics about the medication, the coded information often identifies the manufacturer, the medication's name (sometimes including both the brand and generic names), dosage strength, and expiration date of the medication. There is currently no available mechanism which allows a pharmacist to use this information to automate the prescription filling process. More specifically, although the coded prescription bottles contain all the pertinent information necessary to accurately reconstitute the enclosed medications (i.e., knowing the medication type and dosage strength a pharmacist can access a well-known pharmaceutical reference to determine the amount of filtered water needed to reconstitute the medication) , there is no currently available means for taking advantage of this information for the purpose of automating the medication reconstitution process. Therefore, it is desirable to provide a method and apparatus which can utilize the presently available bar-coded (or otherwise encoded) data to automate the reconstitution process. It is also desirable to provide a method and apparatus which can read the expiration date information and warn the user (typically a pharmacist) that the medication has expired and therefore should not be used.
Accordingly, it is desirable to provide a system which ensures that the proper amount of water is dispensed. Furthermore, it is desirable to provide a system which indicates when filters should be serviced as a function of volume, the duration between the last service, and purity of the water. Additionally, in a pharmaceutical environment, it is desirable to provide a method and apparatus that dispenses the correct amount of filtered water for reconstituting medications based upon coded information about the medications. The present method and apparatus for dispensing fluids provides such a system.